Photosensitive apparatus for sorting translucent objects



H. FRAENKEL July 27, 1965 3 Sheets-Sheet 1 we 51:3 232: um m Allom eysz:

H. FRAENKEL ,Jul 27, 1965 PHOTOSENSITIVE APPARATUS FOR SORTING TRANSLUCENT OBJECTS 3 Sheets-Sheet 2 Filed April 12, 1962 x qilbm thiQR l Inventor k JUMMJ ML flaldwmx 72w Attorneys y 1965 H. FRAENKEL 3,197,647

PHOTOSENSITIVE APPARATUS FOR SORTING TRANSLUCENT OBJECTS Filed April 12, 1962 3 Sheets-Sheet 3 In venlor M M BY 5m;

A llorney:

*2 51:3 USER um E 3,197,647 PHUTGSENLQITIVE AIPARATUS FOR SORTING TRANSLUCENT UBIECTS Herbert Fraenirel, London, England, assignor, by mesne assignments, to Gunsons Sortex Limited Filed Apr. 12, 1962, Ser. No. 187,036

Claims priority, applicatien Great Britain, Apr. 26, 1961,

14,386/ 61 7 Claims. (61. 25ll225) This invention, which concerns the sorting of translucent objects which modify the polarization of polarized light passing through them.

Although the invention is not so restricted, the invention will hereinafter for convenience be described with reference to the sorting of rice grains.

The material within the husk of a rice grain may be white or red in colour. If it is desired to sort the grains according to whether the rice grain is white-centered or red-centered, this may be effected by allowing the grains to fall, one at a time, through a powerful beam of light and allowing the light which has passed through the grains to fall onto light-sensitive means such as a photocell. The amount of light reaching the photocell will be less if the rice grain being viewed is red-centered than if it is white-centered. Accordingly, the photocell may be used to efiect sorting of the white-centered grains from the red-centered grains.

It will be appreciated, however, that whenever there is no grain of rice in the field of View of the photocell, the said powerful beam of light will fall direct onto the photocell and the photocell may receive, say, fifty times as much light as it receives when a rice grain is being viewed. The photocell will therefore be comparatively insensitive to the difference between the amounts of light received when white-centered and red-centered rice grains are being viewed.

According therefore to one particular aspect of the present invention, there is provided a sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine comprising illuminating means for illuminating the translucent objects to be sorted with polarized light, light-sensitive means positioned to receive and be sensitive to light which has passed through a translucent object so illuminated and which has had its polarization modified by said translucent object, means, controlled by signals from the light-sensitive means, for separating desired from undesired translucent objects, an analyser disposed in the path of the light from the objects to the light-sensitive means, the analyser being crossed with respect to the polarization of the polarized light produced by the illuminating means, and means for reducing or eliminating the extent to which the signal produced by Y the light-sensitive means varies with the size of the translucent object being viewed.

The particular ways in which the present invention provides the means for reducing or eliminating the extent to which the signal produced by the light senstitve means varies, will be made clear from the accompanying description and appended claims.

The invention is illustrated, merely by way of example, in the accompanying diagrammatic drawings in which:

FIGURE 1 shows diagrammatically, a sorting machine according to the present invention,

FIGURE 2 shows diagrammatically, an alternative embodiment of a sorting machine according to the present invention, and

FIGURE 3 shows, diagrammatically, yet another embodiment of a sorting machine according to the present invention.

Referring first to FIGURE 1, a sorting machine comprises a light source 30 which is connected'in a circuit including a power supply 31. Light from the light source 30 is collimated by a lens tube 32 and directed through a polarizer 33 which plane polarizes the light and which may be constituted by a sheet of material sold under the The analyser 37, which is adapted to eifect plane po-- larization or" light and which may be constituted by a sheet of material sold under the registered trade mark Polaroid, is crossed with respect to the polarizer 33.

Some of the light-from the light source 30 falls onto a background 40 carried by a background support member 41. The colour of the background 40 is selected to be as close as possible to the desired colour of the objects to be sorted. Light'refiected from the background 40 is reflected by the lightsplitter 36 and directed axially towards the viewing'device 35.

A hopper 42 containing rice grains 43 (or other translucent objects which modify the polarizationof polarized light passing through them) is arranged to discharge the rice grains 43 onto the lower end of a table 44 which extends upwardly towards an endless belt 45. The table 44 is mounted on resilient metal strips46 and is vibrated longitudinally by an electromagnetic vibrator 47. This longitudinal vibration cause the rice grains 43 to move up the table 44 and to fall onto the endless belt 45 which carries them to a point where they may fall freely and one at a time between the light splitter 36 and the analyser 37.

The output of the viewing device 35 is amplified in an amplifier 43 and is then supplied to an electronic comparator 49. The comparator 49 is adapted to distinguish the signals arising from viewing red-centered and white-centered rice grains 43 respectively.

The comparator 49 controls the position of a solenoid valve 50, the valve Sllcontrolling a flow of compressed air through a nozzle 51 extending from a valve body 52.

The valve body 52 is supplied, via a pipe 53, with compressed air from a source (not shown).

The nozzle 51 is positioned so that the putt of air which will pass therethrough when the valve 56 is swiftly opened and closed will remove a red-centered rice grain 43 from the stream of-white-centered grains 43, the red-centered and white-centered grains 43 respectively passing to.

troughs 54, 55.

In operation, the rice grains 43vdrop one at a time from the endless belt 45 and there may therefore be times when there is no grain 43 in the field of view of the viewing means 35. When this occurs the analyser 37 will pre vent substantially any of the light which has been polarized by the polarizer 33 from. reaching the viewing means The value of the signal produced by the viewing means I 35 will thus depend mainly on the ability of the grain 43 to transmit light and thus signals of different value will be received according to whether the grain is red-centered of white-centered. The arrangement may therefore be that if the grain is red-centered, the valve 50 is swiftly opened and closed and the resulting puff of air through the nozzle 51 removes the red-centered grain.

If, however, the operation were merely as so far described, the size of the grains 43 would affect the quality of the sorting since the larger the grain 43 the more light from the polarizer 33 would reach the viewing means 35. This, however, is compensated for by the fact that some of the light from the light source 33 in effect bypasses the polarizer 33 by falling onto the background 40 and by being reflected by the background 40 and the light splitter 36. This light from the background 40, whose intensity is substantially the same as the intensity of the light reaching the viewing means 35 from the polarizer 33, will pass through the analyser 37 at all times. The amount of this light reaching the viewing means 35 will, however, be reduced as the size of a grain 43 being viewed increases. The arrangement may therefore be such that the size of the grain 43 does not appreciably affectthe value of the signal produced by the viewing means 35.

Thus in the absence of a grain 43 from the field of view, the only light falling on the viewing means 35 will be derived from the background 40 and will have a low value. Accordingly the viewing means 35 will never receive the full light from the light source 30 and may therefore be made sensitive to the relatively small differences between-the amounts of light it receives when it views red-centered and white-centered rice grains respectively.

The reflection from the background 49 may be varied by altering its distance from the light source 30 and lightsplitter 36 in any of the ways suggested in British Patent No. 885,286.

In FIGURE 2 there is shown an embodiment of the invention which is the same as that of FIGURE 1 except that no background 4%) or light-splitter 36 is employed and different means are provided to compensate for the differences in the sizes of the grains 43. Parts of the FIGURE 2 embodiment which are the same as those of the FIGURE 1 embodiment are given the same reference numerals and will not be further described.

In the FIGURE 2 embodiment, an infra-red light source 60 is connected to the power supply 31, the light from the infra-red light source 60 being directed onto the grains 43 by way of a lens or lenses 61 and a filter 62, which will transmit only infra-red light.

Between the lens or lenses 38 and the viewing means 35 there is a light splitter 63 which may be constituted by a sheet of glass or a half silvered mirror.

Some of the light falling onto the light splitter 63 from the lens or lenses 38 is directed onto the viewing means 35 while the remainder of the said light is directed, by way of a filter 64 which will transmit only infra-red light, onto an additional photocell or other viewing means 65 which is sensitive to infra-red light only. The viewing means 35, 65 are connected to a difference amplifier 66 the signal from which is passed to the electronic comparator 49 which controls the solenoid valve 59.

The polarizer 33 and analyser 37 are crossed with respect to visible light. When, therefore, a grain 43 is in the field of view, the light reaching the light splitter 63 will be constituted partly by infra-red light reflected by the grain 43 and partly by visible light which has been polarized in one plane by the polarizer 33, depolarized by the grain 43 and polarized in another plane by the analyser 37.

The infra-red light falling on the light splitter 63 will be directed thereby onto the viewing means 35, 65, whereby the viewing means 65 will produce a signal whose value will depend on the size of the grain 43 being viewed. The viewing means 35, however, is arranged to be insensitive to infra-red light and the infra-red light falling on the viewing means 35 will therefore produce no signal.

The polarized visible light falling on the light splitter 63 will be directed thereby towards the viewing means 35, 65, but the fiiter 64 will prevent this light actually reachin the viewing means 65. The amount of polarized visible light failing on the viewing means 35 will be affected by the size of the grain 43. It will therefore be appreciated that the si nal produced by the difference amplifier 66 may readily be arranged to be substantially independent of the size of the grain 43 being viewed.

It will be appreciated that the arrangement shown in FIG. 2 may be used in any case where the light source 30 produces light to which the viewing means 35 (but not the viewing means is sensitive and to which the grains 43 are translucent, while the light source 60 produces light to which the viewing means 35 (but not the viewing means 65) is insensitive and to which the grains 43 are substantially opaque. Thus the infra-red light referred to above may, for instance, be replaced by ultra violet light.

In FIGURE 3 there is shown an embodiment of the invention which is generally similar to that of FIG. 2 and which for this reason will not be described in detail. Parts of the FIG. 3 embodiment which are the same as those of the FIG. 1 embodiment are given the same reference numerals and will not be further described.

In the FIG. 3 embodiment, however, the light sources 30, 60, lens or lenses 63., and filter 62 are omitted, while a light source 70 is used which may consist of one or more lamps and which produces both visible and infrared light. The light, moreover, which has passed through the light splitter 63 passes to the vewing means 35 by way of a light-splitter '71 and a filter 72. The filter 72 passes only light of a certain colour (e.g. red), some of the light falling on the light splitter 71 being directed thereby onto a viewing means 73 by way of a filter 74 which passes only light of a different colour (e.g. yellow). The viewing means 35, 73, which are respectively sensitive to light of the colour which they receive, are connected to a common amplifier 75 where the sum or difference of the signals received from the viewing means 35, 73 can be obtained, the amplifier 75 and viewing means 65 being connected to the amplifier 66.

In the embodiment of FIG. 3, the visible light from the light source 70 which has passed through the polarizer 33, a rice grain 43, the analyser 37, lens or lenses 38 and light splitter 63, is split by the light splitter 71 into two beams which respectively pass by way of the difierently coloured filters 72, 74 onto the viewing means 35, 73 respectively. The amplifier 75, across which the viewing means 35, 73 are connected, will therefore produce a signal representative of the ratio of the amounts of, say, red and yellow in the rice grain 43 being viewed. It will be appreciated that this will enable one to distinguish more readily between the red-centered and white centered rice grains than if a single viewing means 35 is used.

The infra-red light from the light source 70 will, as in the FIG. 2 embodiment fall on the viewing means 65, infra-red light passing at all times, through the polarizer 33 and analyser 37 since these are crossed with respect to visible light only. The filters 72, 74, however prevent this infra-red light from reaching the viewing means 35, 73.

In the FIG. 3 embodiment the rice grain 43 will not reflect the infra-red light but will interrupt it, since the rice grain 43 is opaque to infra-red light. The output of the viewing means 65 will therefore be reduced with increase in the size of the rice grain 43, whereas of course the output of the amplifier 75 is increased with increase in the size of the rice grain 43. The output from the amplifier 66 may therefore readily be arranged to be substantially independent of the size of the rice grain 43 being viewed.

I claim:

1. A sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine comprising illuminating means for illuminating the translucent objects to be sorted with polarized light; light-sensitive means positioned to receive and be sensitive to light which has passed through a translucent object so illuminated and which has had its polarization modified by said translucent object; means controlled by signals from the light-sensitive means for separating desired from undesired translucent objects; an analyser disposed in the path of the light from the objects to the light-sensitive means, the analyser being crossed with respect tot he polarization of the polarized light produced by the illuminating means; and means for irradiating a translucent object with additional light while said object is being viewed by the lightsensitive means and causing the additional light to fall on the light-sensitive means in amount varying in accordance with variation in the sizes of said objects thereby reducing the variation in the signals from the light-sensitive means caused by variation in the sizes of said objects.

2. A sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine comprising first illuminating means for illuminating the translucent objects to be sorted with polarized light; light-sensitive means positioned to receive light which has passed through a translucent object so illuminated and which has had its polarization modified by said translucent object; means controlled by signals from the light-sensitive means for separating desired from undesired translucent objects; an analyser disposed in the path of the light from the objects to the light-sensitive means, the analyser being crossed with respect to the polarization of the polarized light produced by the first illuminating means; a background; and second illuminating means for illuminating the background with unpolarized light, the background being positioned to reflect the unpolarized light in a path interrupted by the translucent object being viewed to fall on the lightsensitive means, the intensity of said unpolarized light at the said light-sensitive means being substantially the same as the intensity of the said polarized light thereat, and the amount of said unpolarized light falling on the light-sensitive means varying in accordance with variation in the sizes of the objects and reducing the variation in said signals from the light-sensitive means caused by variation in the sizes of said objects.

3. A sorting machine as claimed in claim 2 including a light polarizing element; a light splitter optically between said light polarizing element and said analyser; and a single light source positioned to direct light through said polarizing element and said light splitter to said analyser; and a single light source positioned to direct light through said polarizing element and said light splitter to said analyser, and to direct light to said background for being refiected thereby to said light splitter and to be reflected by said light splitter to said analyser.

A sorting machine for sorting translucent objects of various sizes which modify the polarization of the polarized light passing through them, said machine comprising illuminating means for illuminating the translucent objects to be sorted with polarized light; first lightsensitive means positioned to receive and be sensitive to light which has passed through a translucent object so illuminated and which has had its poralization modified by said translucent object; means controlled by signals from the first light-sensitive means for separating desired from undesired translucent objects; an analyser disposed in the path of the light from the objects to the lightsensitive means, the analyser being crossed with respect to the polarization of the polarized light produced by the illuminating means; means for irradiating a translucent object, while said object is being viewed by the first lightsensitive means, with additional light of a wavelength which will pass through said analyser, and to which the first light-sensitive means is not sensitive; second lightsensitive means which is sensitive to and is positioned to receive only said additional light which has passed through the analyser from said object, the amount of additional light reaching the second light-sensitive means varying in accordance with variation in the size of said objects; and means for receiving and correlating the outputs from said first and second light-sensitive means whereby the output from said second light-sensitive means reduces the variation in the signals from said first light-sensitive means caused by variation in the sizes of said objects. 7

5. A sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine comprising first illuminating means for illuminating the translucent objects to be sorted with polarized light; first light-sensitive means positioned to receive and be sendsitive to light which has passed through a translucent object so illuminated and which has had its polarization modified by said translucent object; means controlled by signals from the first light-sensitive means for separating desired from undesired translucent objects; an analyser disposed in the path of the light from the objects to the light-sensitive means, the analyser being crossed with respect to the polarization of the polarized light produced by the first illuminating means; second illuminating means for ir radiating a translucent object, while said object is being viewed by the first light-sensitive means, with additional light which is unpolarized and will pass through said analyser, and to which the first light-sensitive means is not sensitive; second light-sensitive means which is sensitive to and is positioned to receive only said additional light which has passed through the analyser from said object, the amount of additional light reaching the second light-sensitive means varying in accordance with variation in the size of said objects; and means for receiving and correlating the outputs from said first and second lightsensitive means whereby the output from said second light-sensitive means reduces the variation in the signals from said first light-sensitive means caused by variation in the sizes of said objects.

6. A sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine comprising illuminating means for illuminating the translucent objects to be sorted with polarized light; first light-sensitive means positioned to receive and be sensitive to light which has passed through a translucent object so illuminated and which has had its polarization modified by said translucent object; means controlled by signals from the first lightsensitive means for separating desired from undesired translucent objects; an analyser disposed in the path of the light from the objects to the light-sensitive means, the analyser being crossed with respect to the polarization of the polarized light produced by the illuminating means, said illuminating means also irradiating a translucent object, while said object is being viewed by the first lightsensitive means, with additional polarized light of a wavelength which will pass through said analyser at all times, and to which the first light-sensitive means is not sensitive; second light-sensitive means which is sensitive to and is positioned to receive only said additional light which has passed through the analyser from said object, the amount of additional light reaching the second lightsensitive means varying in accordance with variation in the size of said objects; and means for receiving and correlating the outputs from said first and second lightsensitive means whereby the output from said second light sensitive means reduces the variation in the signals from said first light-sensitive means caused by variations in the sizes of said objects.

7. A colour sorting machine for sorting translucent objects of various sizes which modify the polarization of polarized light passing through them, said machine-comprising illuminating means for illuminating the translucent objects to be sorted with polarized light; an analyser and a light splitter successively disposed in the path of light from the illuminating means, the analyser being crossed with respect to the polarization of the polarized light produced by the illuminating means; means for causing objects to be sorted to pass between the illuminating means and the analyser; two light-sensitive members which receive light from the light splitter and which are respectively sensitive to light of different colours; a comparator for comparing the outputs from the two lightsensitive members; means controlled by signals from the comparator for separating desired from undesired objects, said illuminating means also irradiating a translucent object, while said object is being viewed by the two lightsensitive members, with additional polarized light of a wavelength which will pass through said analyser at all times, and to which the two light sensitive members are not sensitive; and a third light-sensitive member which is sensitive to and is positioned to receive only said additional light which. has passed through said analyser from said object, the amount of additional light reaching the third light-sensitive member varying in accordance with variation in the size of said objects, the output from said third light-sensitive member reducing the variation in the signals from said comparator caused by variation in the sizes of said objects.

References Cited by the Examiner UNITED STATES PATENTS 1,945,395 1/34 Cockrell 250--223 X 2,332,308 10/43 Dresser 250-225 X 2,986,066 5/61 Rouy 250-225 X 3,056,033 9/62 Shepard 209-1115 X 3,066,797 12/62 Fraenkel 209-1115 RALPH G. NILSON, Primary Examiner.

2O VJALTER STOLWEIN, Examiner. 

1. A SORTING MACHINE FOR SORTING TRANSLUCENT OBJECTS OF VARIOUS SIZES WHICH MODIFY THE POLARIZATION OF POLARIZED LIGHT PASSING THAROUGH THEM, SAID MACHINE COMPRISING ILLUMINATING MEANS FOR ILLUMINATING THE TRANSLUCENT OBJECTS TO BE SORTED WITH POLARIZED LIGHT; LIGHT-SENSITIVE MEANS POSITIONED TO RECEIVE AND BE SENSITIVE TO LIGHT WHICH HAS PASSED THROUGH A TRANSLUCENT OBJECT SO ILLUMINATED AND WHICH HAS HAD ITS POLARIZATION MODIFIED BY SAID TRANSLUCENT OBJECT; MEANS CONTROLLED BY SIGNAL FROM THE LIGHT-SENSITIVE MEANS FOR SEPARATING DESIRED FROM UNDESIRED TRANSLUCENT OBJECTS; AN ANALYSER DISPOSED IN THE PATH OF THE LIGHT FROM THE OBJECTS TO THE LIGHT-SENSITIVE MEANS, THE ANALYSER BEING CROSSED WITH RESPECT TO THE POLARIZATION OF THE POLARIZED LIGHT PRODUCED BY THE ILLUMINATING MEANS; AND MEANS FOR IRRADIATING A TRANSLUCENT OBJECT WITH ADDITIONAL LIGHT WHILE SAID OBJECT IS BEING VIEWED BY THE LIGHTSENSITIVE MEANS AND CAUSING THE ADDITIONAL LIGHT TO FALL ON THE LIGHT-SENSITIVE MEANS IN AMOUNT VARYING IN ACCORDANCE WITH VARIATION IN THE SIZES OF SAID OBJECTS THEREBY REDUCING THE VARIATION IN THE SIGNALS FROM THE LIGHT-SENSITIVE MEANS CAUSED BY VARIATION IN THE SIZES OF SAID OBJECTS. 